Esters of polyhydroxy-benzoic acids



This application ismade under the act of Patented Sept. 27, 1949 IIS'IIERS OF POLYHYDROXY-BENZOIC ACIDS Steward Gin Morris, Philadelphia, and Roy W.

Riemenschneider, glenside, Pas, assignors to the United, States of America as represented bythe Secretary of Agriculture NoDrawing. Applica on June 21,1946,

' Serial No. 678,188

Claims. (Cl. 260-7473) ,(Grantedsunderl the act of March 3;1883, as

, amended April 30, 1928';- 370 0, Gn'f-75'7) chloride tribenzyl'ethr can be obtained by other March 3, 1883, as amended by the act of April 30, methods, foi ins ta nce, benzylation of gallic 1928, and the invention herein described-if patented, may be manufacturedand used by or for the Government of the United States of America for governmental purposeswithout the Payment to us of any royalt thereon.

This invention relates to esters of polyhydroxy-benzoic acids, more particularly to the higher alkyl esters of gallic acid and has for its object the production of these esters.

Gallic acid esters of the lower fatty alcohols can be obtained by direct esterification in the presence of catalysts such as concentratedusulthis procedure ;is used in an attempt to bring about esterification of gallic acid with higher aliphatic alcoholscontaining more than six carbon atoms in the molecule the corresponding esters are not formed or the reaction yields only a very small amount of impure products.

We have found that alkyl esters of gallic acid containing six or more carbon atoms in the alkyl radical can be obtained by the following procedure. Gallic acid is converted to galloylchloride tribenzyl-ether'which is reacted with an aliphatic alcohol containing six,or more carbon atoms per gallic acid ester, which on hydrogenation yields acid to form the benz'yl ester of tribenzyl gallic acid, followed by sapqnification of the ester group 5 d.- scc ntcqs as sm Qi h car n group with a carrier such as for in ance' ch arcoall furic acidor anhydrou hydm n lfl W 1 yen lii ar li s ie'.iq ei9 Wi of the higher anal esters o f lgallic acid from the .of tr be zyl gallic acid oblloyll $513], ride triben zyl ether co olswhensubjected to cata yr cna caar e at i ezdq lblel'lh ll ig theallsr e l ra lism at 1. .itheisamel time .cehenzxlatc rie i i... b spondmgalkyliestersQfigalhc acid. I i Wen-haves found ,cthatmour invention also orreapplicable to the production of long chain alkyl molecule to form the corresponding tribenzylesters 9 Owen polyhydroxybenzqic-afiidisllch as foflexampl protocatechuicacid. t Alkylcesters of polyhydroizybenzoic acid containing atleast six the gallic acid alkyl ester as shown by the follow- I, i I I carbon atoms the a1ky1-radical are useful as ining equations:

We prefer to conyertgallic acid to galloyl chloride tribenzyl-ethercby first preparing methylgallate,

benzylating-itto :obtain the methyLesterof tribenzyl gallic acid, saponifying the ester group ;to.fo1m gallic. acidtribenzyl ether and converting this compound to galloyl chloride tribenzyl ether -,t m di c ia he.- pmsll 9i qn .qim ii 5o o c eir a eflmbr readi sqlu l n ily by. treating it:-;with ,thionyl chloride, 5}alloyl 55'July 253 1946.

Among our new products are those of the following formula: I

oo-o-cmR in which CH2R is an alkyl hydrocarbon radical having a straight chain of at least seven carbon atoms, a: being an integer not exceeding two. In a preferred group the straight chain has at least twelve carbon atoms.

The invention is further characterized as including n-alkyl esters of gallic acid containing at least seven carbon atoms, and preferably at least twelve carbon atoms, in the alkyl radical.

As illustrative embodiments of a manner in which our invention may be carried out in practice the following examples are given.

Example I A solution obtained by heating 250 grams of commercial gallic acid (containing one molecule of crystallization water) with 750 cc. methyl alcohol, is saturated with hydrogen chloride at 0 C. and allowed to stand overnight at this temperature. Approximately 400 cc. of the solvent are then distilled off and on cooling the distillation residue to 0 C. methyl gallate is obtained as a crystalline precipitate.

Fifty-nine grams of the methyl gallate so obtained are dissolved in 250 cc. of anhydrous acetophenone, 142 grams of dry powdered potassolved in cc. of water, and 350 cc. ethyl alcohol. The solution thus obtained is poured into 1500 cc.

of cold water containing 20 cc. of concentrated hydrochloric acid. The precipitate consisting of gallic acid tribenzyl ether is filtered off and crystallized from absolute alcohol-benzene mixture. The product so obtained has a melting point of 195 C. The yield is 49 grams.

Example II A mixture of 49 grams gallic acid tribenzyl ether and 135 cc. thionyl chloride is heated first at 50 C. for about minutes, then the temperature is raised to 60 C. over a period of approximatelyl hours. Excess thionyl chloride is then distilled off at the water pump While maintaining the temperature at 60 C. To remove traces of thionyl chloride the distillation residue is dissolved in benzene and again evaporated to dryness. The galloyl chloride tribenzyl ether thus obtained is crystallized from benzene-petroleum ether. The yield is 46.5 grams of galloyl chloride tribenzyl ether melting at, 116.5 C.

Example III Ten grams of galloyl chloride tribenzyl ether prepared as described in Exampl II, and 8.12

4 grams of lauryl alcohol are melted at 120 C. and the mixture is heated at C. for approximately one hour. The lauryl ester of tribenzylgallic acid thus obtained is crystallized from petroleum ether (boiling range 30-70 C.) The yield is 12.9 grams of a product melting at 71.5-'72 C.

Emample IV Eleven and twenty-five hundredths grams lauryl ester of tribenzyl gallic acid prepared as described in Example III and a hydrogenation catalyst prepared by reducing 1 gram palladium chloride on 6 grams of charcoal, as described by Ott and Schroeter (1927 Ber. 60, 633), are added to approximately 150 cc. of absolute alcohol. The mixture is heated to dissolve the ester, and is then hydrogenated under approximately 45 pounds hydrogen pressure. The reaction is usually completed within five to ten minutes. The solution is filtered to remove the catalyst and evaporated to dryness on a water bath and under reduced pressure. The lauryl gallate thus obtained consists essentially of n-dodecyl ester of gallic acid which on crystallization from petroleum etherbenzene solvent has a melting point of 96.5-97 C.

Example V By following the procedure described in Example IV and replacing the lauryl alcohol used in that example by the equimol'ecular amount of any one of the following alcohols:

n-Hexyl alcohol n-Octyl alcohol n-Tetradecyl alcohol (myristyl alcohol) n-Hexadecyl alcohol (cetyl alcohol) n-Octadecyl alcohol (stearyl alcohol) the corresponding alkyl esters of trib'enzyl-gallic acid are obtained,

Melting point, C.

n-I-Iexyl ester 72-73 n-Octyl ester 74.5 n-Tetradecyl ester 75.5-76 n-Hexadecyl ester 79.5-80 n-Octadecyl ester 83.5-84

Example VI Debenzylation by catalytic hydrogenation as described in Example IV using instead of lauryl ester of tribenzyl-gallic acid, the equimolecular amount of any one of the alkyl esters described in Example V yields the corresponding esters of gallic acid.

Melting point, C.

n-Hexyl gallate 93.5 n-Octylgallate 1 94-95.? n-Tetradecyl gallate 98.5-99.2 n-Hexadecyl gallate 99.5- n-Octadecyl gallate 104.5

Hydrogenation may be conducted at 35-45 pounds pressure.

/ Example VII Six and nine-tenths grams of oleyl alcohol are added to 9.1 grams of galloyl chloride tribenzyl ether prepared as described in Example II. The mixture is heated at C. for 3 hours and the product thus obtained consisting essentially of oleyl alcohol-ester or tribenzyl gallic acid on grystallization from petroleum ether melts at The oleyl alcohol ester of tribenzyl gallic acid thus obtained is dissolved in cc. of warm ethyl alcohol, and hydrogenated in the presence of 0.3 gram of platinum catalyst prepared as described in Gilman and Blatts Qrganic Syntheses (Collective volume I, second ed. 1941, page 463), at about 42 pounds hydrogen pressure. On completion of the hydrogenation the solution was filtered, and the solvent evaporated. The residue crystallized from benzene-petroleum ether has a melting point of 103.5-104.2 C. and consists of octadecyl gallate.

Analogous results are obtained using other hydrogenation catalysts such as palladium on charcoal.

Having thus described our invention, we claim:

1. The process of producing an alkyl ester of an acid of the group consisting of gallic acid and protocatechuic acid which comprises reacting a compound of the group consisting of galloyl chloride tribenzyl ether and protocatechuic acid chlorid'e-dibenzyl ether with a primary monohydric alcohol and de-benzylating by subjecting the resulting ester to catalytic dehydrogenation.

2. The process of producing alkyl esters of gallic acid containing at least six carbon atoms in the alkyl radical which comprises reacting galloyl chloride tribenzyl ether with a primary aliphatic alcohol containing at least six carbon atoms per molecule, to form the tribenzyl gallic acid ester of said alcohol and then de-benzylating without de-esterifying by subjecting said ester to catalytic hydrogenation.

3. The process as defined in claim 2 wherein the primary aliphatic alcohol is a saturated alcohol.

4. The process as defined in claim 2 wherein the primary aliphatic alcohol is a saturated alcohol containing from 6 to 18 carbon atoms per molecule.

5. The process of producing n-dodecyl ester of gallic acid which comprises reacting galloyl chloride tribenzyl ether with n-dodecyl alcohol to form the n-dodecyl ester of tribenzyl gallic acid and then de-benzylating without de-esterifying by subjecting said ester to catalytic hydrogenation.

6. The process of producing n-tetradecyl ester 7 of gallic acid which comprises reacting galloyl chloride tribenzyl ether with n-tetradecyl alcohol to form the n-tetradecyl ester of tribenzyl gallic acid and then de-benzylating without de-esterifying by subjecting said ester to catalytic hydrogenation.

7. The process of producing n-octadecyl ester of gallic acid which comprises reacting galloyl chloride tribenzyl ether with n-octadecyl alcohol to form the n-octadecyl ester of tribenzyl gallic acid and then debenzylating without de-esterifying by subjecting said ester to catalytic hydrogenation. I

8. The process as defined in claim 2 in which the primary aliphatic alcohol is a monohydric alcohol.

9. The process described in claim 2 in which the catalytic hydrogenation is with hydrogen gas under pressure in the presence of palladiumcharcoal catalyst.

10. The process described in claim 5 in which the catalytic hydrogenation is with hydrogen gas under pressure in the presence of palladiumcharcoal catalyst.

11. The process described in claim 10 in which the hydrogenation is in absolute alcohol.

' STEWARD G. MORRIS.

ROY W. RIEMENSCHNEIDER.

REFERENCES CITED The following references are of record in the file of this patent:

Chem. Abstracts, vol. '27 

